GdfidL computes electromagnetic Fields in 3D-Structures using parallel or scalar Computer Systems. GdfidL computes Resonant Fields in lossfree or lossy Structures and Time dependent Fields in lossfree or lossy Structures. The Fields may be excited by Port Modes or relativistic Line Charges. The Postprocessor computes from these Fields eg. Scattering Parameters, Wake Potentials, Q-Values and Shunt Impedances.